Gabriele asserted his innocence Tuesday when he was asked by his lawyer about the theft charge, according to a pool of selected journalists allowed into the courtroom. The Vatican penal system does not require a formal plea.

But, he said: "I feel guilty of having betrayed the trust that the Holy Father gave me."

The former butler added that he felt he was "the closest layman to the pope."

Computer technician Claudio Sciarpelletti, who worked in the Vatican's secretariat of state, is accused of complicity in the crime. The court will try him separately, once the former butler's trial is finished.

If convicted of aggravated theft, Gabriele could face up to eight years in an Italian prison, although it is possible the pontiff could choose to pardon him. Sciarpelletti would face a shorter prison term of only a few months if found guilty.

Questioned by Dalla Torre about how and why he had collected the documents, Gabriele said he had started photocopying them in 2010.

He said his "intention was to find a person he could fully trust to whom to vent .... about the disconcerting atmosphere in the Vatican, felt not only by me. This feeling of bewilderment was widely felt in the Vatican."

Gabriele said he had made the photocopies during regular working hours and in front of other people who worked in the same office.

He told the court that he used his "instincts" in choosing what to photocopy.

He said he had received no money or any other benefit from the person to whom he gave the documents, adding that this "was the essential condition of our agreement."

Gabriele also said that "the book was certainly not something he wanted."

A prosecutor in the case said in a report last month that Gabriele had acted out of a desire to combat "evil and corruption everywhere in the Church."

"I was certain that a shock ... would have been healthy to bring the church back onto the right track," Gabriele is quoted as saying by the prosecutor, Nicola Piccardi.

Asked Tuesday about a gold nugget belonging to the pope that was found by police who searched his apartment, Gabriele told the court he hadn't known it was there.

The officers who carried out the search said the nugget was 3-4 centimeters (just over an inch) long and had been discovered in a shoebox, along with a signed check made out to the pontiff.

The court heard Saturday that 82 boxes of evidence were removed from Gabriele's apartments in Vatican City and Castel Gondolfo, a small town near Rome.

Also Tuesday, the pope's personal secretary, Monsignor George Gaenswein, testified that he never "had any reason to doubt" Gabriele.

More witnesses will be heard in the case Wednesday.

Recalling his initial detention in May, Gabriele told the court that when he was first arrested he was put in a cell so small he couldn't open his arms out to their full extent.

He was later moved to another, larger cell, Gabriele said. However, in this cell, where he was held for 15 to 20 days, the light was kept on 24 hours a day with no means for him to turn it off, he said. Gabriele said his eyesight had been damaged as a result.

The Vatican prosecutor's office has opened an investigation into his claims of poor treatment in detention.

But Jesuit Father Federico Lombardi, head of the Holy See media office, told reporters in a briefing after the court session that the cells used by the Vatican meet international standards.

Lombardi also suggested that the allegations by Gabriele's defense lawyer that his client had been inhumanely treated seem questionable, since they were only coming out now.

A statement from the Vatican Police said the force had been in the process of upgrading its long-term cells when Gabriele was arrested. The work was accelerated and he was moved to a more comfortable cell after 20 days, the statement said.

The Vatican cells meet the standards present in other countries for similar situations, the statement said. It added that Gabriele had asked for the light to be left on to keep him company at night, and that he had been provided with eye masks.

Gabriele was given access to medical staff and a spiritual adviser, as well as being allowed to attend mass with his family, the statement added.

Gabriele, wearing the same gray suit he had on for Saturday's initial hearing, appeared more relaxed Tuesday, smiling, closing his eyes briefly and intermittently chewing either gum or candy, according to the journalist pool.

In the previous hearing Gabriele had appeared pale as he sat largely expressionless in the courtroom.

Both sessions were held under closely controlled conditions, with only a handful of approved reporters allowed to attend. They were required to brief other journalists.

On Saturday, the admitted journalists were made to hand over their own pens in exchange for Vatican-issue ones in case any contained concealed recording devices.

Gabriele's family did not attend either session.

The former butler's lawyer, Christiana Arru, filed objections concerning the admissibility of evidence Saturday, including the results of a psychological exam conducted without the presence of his lawyer and footage gathered via a hidden camera, some of which the court accepted.

Gabriele's case is thought to be the most significant ever heard in the Vatican City courthouse, which has handled mostly petty theft cases in the past.

A Vatican legal expert, Cardinal Velasio De Paolis, said in an interview published Sunday in Italian newspaper La Repubblica that popes in the past have typically granted pardons in the face of sincere confessions and repentance.

The Vatican City State penal code for proceedings involving its citizens is based on the Italian penal code of the second half of the 19th century. Dalla Torre will lead the debate in the courthouse, located behind St. Peter's Basilica, and question the defendant directly.

Prison terms handed down by the court are served in the Italian prison system, under an agreement between the Vatican City State and Italy.

Gabriele was arrested in May, following a top-level Vatican investigation into how the pope's private documents appeared in the best-selling book "Sua Santita" ("His Holiness"), by Italian journalist Gianluigi Nuzzi.

The Vatican called the publication of his book "criminal" when it was released in Italian.